Micro Linear Corporation ML4423CS, ML4423IP, ML4423IS, ML4423CP Datasheet

July 2000

ML4423*

1, 2, or 3-Phase Variable Speed AC Motor Controller

GENERAL DESCRIPTION

The ML4423 provides the PWM sinewave drive signals
necessary for controlling three phase AC induction motors as
well as single and two phase split capacitor AC induction
motors.

A constant voltage/frequency ratio can be maintained
over a frequency range of greater than 10:1, providing
15Hz to 150Hz control. The output variable frequency AC
voltages are sensed and fed back to the controller to track the
sinewave frequency and amplitude set at the speed control
input. Direction, on two and three phase motors, is controlled
by changing the relative phase difference between the motor
windings: 90× for two phase motors and 120× and 240× for three
phase motors.

To protect the motor, power devices, high voltage drivers
and control circuitry, the ML4423 includes fixed period,
pulse by pulse variable duty cycle current limit, deadtime
circuitry, and undervoltage lockout. The ML4423 has
selectable output voltage swing of 5V or 12V for
interfacing to different high side drivers and power devices.

FEATURES

■ Drives single, two, and three phase AC motors

■ Greater than 10:1 variable speed control range

■ Constant V/F ratio with programmable end points

■ Reverse capability for two and three phase motors

■ Low distortion PWM sinewave drive

■ Eliminates run capacitors in PSC motors

■ Coast function for quick power disable

■ Low cost interface for various gate drivers

■ PWM current limit, undervoltage lockout, and

programmable deadtime

■ 12V ±20% operation with onboard 8V reference

(* Indicates Part Is End Of Life As Of July 1, 2000)

BLOCK DIAGRAM

FB A

1

FB C

2

FB B

3

C

12

V

5

V

4

R

6

O

SPEED

MIN

SPEED

+
–

+
–

+
–

+
–

SPEED

CONTROL

SINE A-C

27

GENERATOR

GENERATOR

28

SINE A

SINE B

SINE B-C

GENERATOR

13

PWM

OSCILLATOR

SINE C

F/R

PWM

SINE

WAVE

CONTROL

18

3PH/2PH

UVLO

26

COAST

14

R

DT

9

5V/12 SELECT

GATING

LOGIC

&
OUTPUT
DRIVERS

+

COMP

–

REFERENCE

V

DD

GND R

17 8 7

REF

I

SENSE

0.5V

V

REF

HA

HB

HC

LA

LB

LC

25

24

22

23

21

19

20

16

C

T

15

1

ML4423

PIN CONFIGURATION

ML4423

28-Pin Narrow PDIP (P28N)

28-Pin SOIC (S28)

SENSE A

SENSE C

SENSE B

V

MIN

V

SPEED

R

SPEED

V

REF

R

REF

R

DT

SINE A-C

1

2

3

4

5

6

7

8

9

10

28

C

GM2

27

C

GM1

26

V

DD

25

5V/12V SELECT

24

HA

23

HC

22

HB

21

LA

20

LC

19

LB

SINE B-C

C

C

COAST

11

12

O

03

T

14

TOP VIEW

18

17

16

15

3PH/2PH

GND

I

SENSE

F/R

2

PIN DESCRIPTION

ML4423

PIN NAME FUNCTION

1 FB A Differential input which, in

conjunction with FB C, feeds back the
voltage applied across motor winding
A-C.

2 FB C Input which feeds back the voltage

applied to motor winding C. Reference
voltage for windings A and B.

3 FB B Differential input which, in

conjunction with FB C, feeds back the
voltage applied across motor winding
B-C.

4V

MIN

The voltage on this pin sets the
minimum sinewave amplitude at low
speeds.

5V

SPEED

The voltage on this pin sets the
frequency and amplitude of the
sinewaves generated at SINEA and
SINEB.

6R

SPEED

An external resistor to ground provides
a variable current to the sinewave
generator. The current is proportional
to V

SPEED

.

PIN NAME FUNCTION

13 C

T

An external capacitor to ground sets
the PWM triangle frequency in
conjunction with the external resistor
R

.

REF

14 COAST A logic low input causes all output

drive transistors to turn OFF. An
internal pull-up drives COAST to V
if left unconnected.

15 F/R A logic high input causes phase A to

lead phase B, while a logic low input
causes phase A to lag phase B. An
internal pull-up drives F/R to VDD if
left unconnected.

16 I

SENSE

Motor current sense input.

17 GND Signal and power ground.

18 3PH/2PH Leaving this pin unconnected selects

3-phase drive. Connecting this pin to
VDD selects single/2-phase drive.

19 LB Low side drive output for phase B.

20 LC Low side drive output for phase C.

DD

7V

8R

REF

REF

8V reference output which can be
used for setting V

SPEED

and V

An external resistor to ground provides
a constant current used for setting the
PWM frequency in conjunction with
CT.

9R

DT

An external resistor to ground sets the
deadtime in the output stage to
prevent cross-conduction in the power
devices.

10 SINE A-C A test output for observing the

internally generated sinewave used for
motor winding A-C.

11 SINE B-C A test output for observing the

internally generated sinewave used for
motor winding B-C.

12 C

O

An external capacitor to ground sets
the sinewave frequency in conjunction
with V

SPEED

and R

SPEED

.

MIN

21 LA Low side drive output for phase A.

.

22 HB High side drive output for phase B.

23 HC High side drive output for phase C.

24 HA High side drive output for phase A.

25 5V/12V Input to select 5V or 12V output drive.

SELECT Leaving this pin unconnected selects

5V output drive levels at the driver
outputs. Connecting this pin to V

CC

selects 12V output drive levels at the
driver outputs.

26 V

27 C

DD

GM1

12V power supply input.

An external capacitor to ground sets a
pole in the feedback loop.

28 C

GM2

An external capacitor to ground sets a
pole in the feedback loop.

3